#include <cstring>
#include <iostream>
#include <algorithm>

using namespace std;

const int N = 510, INF = 0x3f3f3f3f;

int n, m;
int g[N][N];
int dist[N];
bool st[N];

int prim()
{
    memset(dist, 0x3f, sizeof dist);
    int res = 0;
    dist[1] = 0;
    for(int i = 0; i < n; i ++)
    {
        int t = -1;
        for(int j = 1; j <= n; j ++)
            if(!st[j] &&(t == -1 || dist[t] >dist[j]))
                t= j;
        if(dist[t] == INF) return INF;
        res += dist[t];
        st[t] = true;
        for(int j = 1; j <= n; j ++)
            dist[j] = min(dist[j], g[t][j]);
    }
    return res;

}
int main(){
    scanf("%d%d", &n, &m);
    memset(g, 0x3f, sizeof g);
    while(m --)
    {
        int a, b, c;
        scanf("%d%d%d", &a, &b, &c);
        g[a][b] = g[b][a] = min(g[a][b], c);

    }
    int t = prim();
    if(t == INF) puts("impossible");
    else cout<<t<<endl;

    return 0;
}